When manufacturing circuitry, after attaching components to a substrate, such as to a circuit board or flexible material, it is desirable to perform testing. These tests, among other things, are to make sure that circuit connections have been properly made, are sufficiently conductive, and are not cold connections. Such testing is known in the art as "in-circuit" testing. It is difficult to perform such testing while power is supplied to the circuitry, such as by an on board cell or battery.
In circuit testing is performed for a wide variety of types of circuitry. Just one example of circuitry for which in circuit testing is performed is in identification circuitry.
As large numbers of objects are moved in inventory, product manufacturing, and merchandising operations, there is a continuous challenge to accurately monitor the location and flow of objects. Additionally, there is a continuing goal to interrogate the location of objects in an inexpensive and streamlined manner. One way of tracking objects is with an electronic identification system.
Some such systems generally include an identification device including circuitry provided with a unique identification code in order to distinguish between a number of different devices. Typically, the identification devices are entirely passive (have no power supply). However, this identification system is only capable of operation over a relatively short range, limited by the size of a magnetic field used to supply power to the devices and to communicate with the devices.
Another type of electronic identification system, and various applications for such systems are described in detail in commonly assigned U.S. patent application Ser. No. 08/705,043, filed Aug. 29, 1996, and incorporated herein by reference. The system includes an active transponder device affixed to an object to be monitored which receives a signal from an interrogator. The device receives the signal, then generates and transmits a responsive signal. Because active devices have their own power sources, they do not need to be in close proximity to an interrogator or reader to receive power via magnetic coupling. Therefore, active transponder devices tend to be more suitable for applications requiring tracking of a tagged device that may not be in close proximity to an interrogator. For example, active transponder devices tend to be more suitable for inventory control or tracking.
Electronic identification systems can also be used for remote payment. For example, when a radio frequency identification device passes an interrogator at a toll booth, the toll booth can determine the identity of the radio frequency identification device, and thus of the owner of the device, and debit an account held by the owner for payment of toll or can receive a credit card number against which the toll can be charged. Similarly, remote payment is possible for a variety of other goods or services.
Testing of battery powered circuitry of this or other types typically requires delaying connection of the battery to the circuit until in circuit testing is completed. Then, another in circuit test must be performed to verify the battery connections.